Researchers at Northwestern University have developed 3D printed neurons that can send signals to real brain cells and get a response back. According to the team, the printed structures could “talk” to living neurons. It’s an early result, but it builds on years of progress in bioprinting and adds to ongoing efforts to make bioprinted systems more functional.

For years, scientists have been able to 3D print materials that resemble parts of the human body. In some cases, they’ve even printed living cells into organized structures. But making those printed systems behave like real tissue, especially something as complex as the brain, has remained a major challenge.

Beyond biology, the work is also tied to the broader goal of developing more efficient, brain-like computing systems. By mimicking how neurons signal — a key feature of the brain, which is the most energy-efficient computer known — futuristic systems could perform complex operations using far less power than today’s data-hungry technologies.

Mark Hersam wins 2024 mid-career research award. Image courtesy of Northwestern University.

Neurons carry signals through the brain, controlling everything from movement to memory. The question for the researchers was whether a 3D printed version could do something similar, send signals, and interact with real brain cells. 

In their study titled Printed MoS₂ memristive nanosheet networks for spiking neurons with multi-order complexity, published in the journal Nature Nanotechnology, the team led by Mark Hersam, a materials science expert at Northwestern University focused on brain-like computing, describes how they used aerosol jet printing to build tiny, nanoscale electronic networks designed to behave like neurons. 

The system is made using electronic inks based on soft materials like molybdenum disulfide and graphene, printed onto a flexible polymer surface rather than on traditional rigid silicon, explains Hersam. The printed neurons were placed next to living brain cells taken from mice and kept alive in the lab, not inside a live animal. Then, the printed neurons sent signals, and the real neurons responded. In other words, the two systems, one printed, one biological, were able to communicate.

The result is part of a broader effort to create printed systems that can interact directly with real brain cells and real living tissue, mimicking natural behavior. The brain is especially difficult because it depends on constant, precise communication between neurons. Even small disruptions can change how those signals are processed. But by showing that printed neurons can trigger responses in real brain cells, the researchers are demonstrating that 3D printed systems can start to take part in that communication network. It’s still early, and the setup is controlled and limited, but it points to what could be possible.

The work marks a step toward electronics that can communicate directly with the nervous system, with potential applications in brain-machine interfaces and neuroprosthetics, including implants for hearing, vision, and movement. These devices connect directly to the brain to send or receive signals, but today they rely on traditional electronics. If printed components can work more naturally with brain tissue, they could lead to interfaces that are easier for the body to accept and more effective.

There are also implications for treating neurological conditions. If scientists can learn how to guide and control communication between printed and real neurons, it could eventually support efforts to repair damaged areas of the brain, including cases where neural connections are lost or disrupted.

What’s more, there’s growing interest in building systems inspired by how the brain processes information, often referred to as neuromorphic computing. Work like this, which blends biological behavior with engineered structures, hints at new ways of thinking about how such systems could be built in the future.

“The world we live in today is dominated by artificial intelligence (AI),” said Hersam. “The way you make AI smarter is by training it on more and more data. This data-intensive training leads to a massive power-consumption problem. Therefore, we have to come up with more efficient hardware to handle big data and AI. Because the brain is five orders of magnitude more energy efficient than a digital computer, it makes sense to look to the brain for inspiration for next-generation computing.”

Mark Hersam elected to the National Academy of Engineering. Image courtesy of Northwestern University.

Researchers have been moving in this direction for some time. In recent years, teams such as those at Monash University have used 3D bioprinting to create networks of living brain cells that can grow and communicate, mainly for studying disease and testing drugs. At the same time, others have developed artificial neurons using electronic components, such as memristors, to mimic how the brain processes information for computing applications. But what makes the Northwestern University work different is that it brings these two approaches closer together, so that instead of printing living cells or building traditional rigid electronics, the team created printed electronic systems that behave like neurons and can directly interact with real brain tissue.

As advanced as this study is, it is not a fully functional artificial brain, nor is it something that can be implanted or used clinically today. The interaction demonstrated here is a first step, showing that communication is possible under controlled conditions. There is still a long way to go before this can translate into real-world applications.